I remember that one unit I either owned, or considered. Needed 25 PSI inlet. or it would not run. Some where in my memory, I think it was a gas power unit I either borrowed, or wished I had.
The electric unit I have now. One time when my parents cellar flooded, I used it to help move water. Rated 1.3 GPM. But, with no nozzle, I'd guessed it ran more like
2.0 or better GPM. I had to pour water into the inlet tube, and then stuff it quickly into the water source. It wasn't self priming.
Pressure washers only run cold water. Because they rely on the water flow to help cool the pump.